As a mechanical engineer who has worked in the industry, I'd tend to be very selective about aftermarket exhausts for the C8, and I think there are only 2 exhaust types I'd fit to my C8: OEM, Borla.
The factory performance exhaust was designed and built by a German company called Tenneco, and it was very well designed from the aspects of durability, heat shielding, noise. With the valves open IIRC it barely comes in under most legal noise limits. If you like louder? That's fine... The factory flex joints are designed to take years of use, whereas many "universal" flex joints as used on a lot of aftermarket exhausts have not been designed for the specific bending moments of the C8, which could in turn reduce reliability. A lot of work went into the heat shielding on the OEM exhausts because heat management is an issue on the C8. Many aftermarket exhaust manufacturers will claim their exhaust are just fine without heat shielding, but wiring harnesses and hoses sometimes take years to rot out due to heat exposure. Fine on a race car, your choice if you drive in stop and go traffic with everything getting heat soaked, and you're keeping the C8 long term. Finally performance, a lot of aftermarket companies claim performance gains and weight savings, however in the real world after the ECU readjusts a lot of times gains will be less than initially present at installation, and marginal at best over the factory performance exhaust. Most weight savings are due to a lack of heat shielding.
Borla is the only aftermarket company that I know of that has put the time and engineering into designing exhausts for the C8 that match OEM requirements for heat shielding, and flex joint durability, and IIRC Borla makes the only aftermarket exhaust option offered by GM for the C8.
Some info on the engineering that went into the factory performance exhaust:
Tenneco C8 Corvette active exhaust system Dmitri Konson Megan Wikaryasz
www.sae.org
Borla videos on the C8 exhaust where David Borla discusses the challenges in meeting OEM specs, and how they were able to do it on their own exhausts:
Any other companies taking the same care and attention to detail as Tenneco or Borla to ensure long term reliability?